1. Field of the Invention
The invention relates to a drive unit for a door or a gate, particularly a garage door, having an electric motor.
2. Description of the Related Art
EP 0 500 984 B1 describes a drive unit for a garage door, which is equipped with four terminal limit switches. In this case, the drive shaft protruding from the gear is provided with a pinion, which, on the one hand, drives the revolving chain and, on the other hand, is designed such that a bevel gear pinion simultaneously drives a terminal limit switch unit. In this case, the terminal limit switch unit is placed adjacent to the drive shaft and substantially consists of a threaded spindle which is equipped with adjusting nuts. The adjusting nuts are fixed by means of a holding device such that, while rotating the drive shaft, the spindle is rotated simultaneously and therefore the adjusting nuts are guided along the threaded spindle. Thus, they can trigger the corresponding electric contacts.
The position finding of the gate according to EP 0 500 984 B1 is realized exclusively at predetermined, precisely defined locations, preferably in the respective final positions via the corresponding terminal limit switches, which automatically turn the drive unit on and off. This means that, in terms of control, only this information regarding the predetermined positions are forwarded to the control unit. Any required intermediate positions can neither be detected nor controlled, such that there is no possibility for manipulating the sequence of movements of the gate, because the adjustment of the position of the terminal limit switches can only be done manually.
There are many different types of drive units for a door or a gate available on the market. They particularly differ from each other by the different performance data thereof, i.e. there are variably powerful drive units for large or small doors and gates. These drive units must be equipped with different safety devices, such as light barriers or terminal strips or a power limit control for the drive motor, etc. As a rule, a maximum driving force is mandatory, to prevent people from being injured and equipment from being damaged. This leads, however, to a large variety of different drive units, which is not only complicated and costly from the manufacturing point of view, but also for stock keeping and logistics. Hence, in extreme cases, this may lead to circumstances where it is difficult to figure out the appropriate drive unit, whereby even unsuitable decisions may be made and may in turn lead to further increasing costs and loss of time.